1. Field of the Invention
The present invention relates to a circuit board, a filter circuit including the circuit board, and a capacitance element, and particularly relates to a circuit board mounted with a capacitance element, a filter circuit including the circuit board, and a capacitance element provided with a circuit.
2. Description of the Related Art
As a measure against noise of an electronic device, a filter circuit is often used. Examples of this filter circuit include an EMI (Electro-Magnetic Interference) removal filter. The filter circuit is a circuit that allows passage of a necessary component and removes an unnecessary component in a current flowing in a conductor, and a capacitor being a capacitance element may be used in a configuration of the circuit. It is known that in the filter circuit using the capacitor, a noise reduction effect deteriorates due to equivalent series inductance (ESL) that is parasitic inductance of the capacitor.
Meanwhile, there is known a configuration of an antenna device in which an effective inductance component of an antenna element is reduced by using a pseudo negative inductance component of an impedance converter circuit (e.g., Japanese Patent Application Laid-Open No. 2012-85251).
However, when the parasitic inductance of the capacitor is to be canceled by using the impedance converter circuit shown in Japanese Patent Application Laid-Open No. 2012-85251, there have been cases where the parasitic inductance of the capacitor cannot be sufficiently canceled by simply using the impedance converter circuit for the filter circuit. Especially in the case of manufacturing a circuit board to cancel the parasitic inductance of the capacitor, it has been necessary to consider manufacturing variations in the circuit board.